The invention relates to the production of hydrogen and carbon monoxide-containing gas from carbonaceous fuels. More particularly the invention is directed to a two stage partial combustion process affording increased yields of CO and H.sub.2 which is especially applicable to conversion of finely dispersed solid carbonaceous fuels such as coal or coke.
In the chemical and energy providing industries there is a great demand for gas containing substantial amounts of H.sub.2 and/or CO in various mixtures and purities. Such gas may be used, for instance, as a starting material for the manufacture of chemical products -- e.g., ammonia, alcohols, etc., -- as a reducing agent, as a clean fuel or in hydrogenation processes. A well-known and widely employed method for the preparation of such a gas is the partial combustion of carbonaceous fuels in a substantially void or hollow reactor. As a general matter, prior efforts to optimize this partial combustion process have concentrated on reactor designs and reactant mixing procedures and devices wherein gaseous or finely dispersed carbonaceous fuel is reacted with oxygen diluted with nitrogen and/or steam in a single reaction stage or zone. Despite the several advances made in this area of technology, the utilization of such single stage partial combustion processes is still not considered to be entirely satisfactory because the high temperatures required for carrying out the reaction in a single stage generally result in a high oxygen consumption which in turn leads to a relatively low yield of CO and H.sub.2. Other two stage processes require that the solid carbonaceous fuels be introduced in the form of a slurry usually with other liquid hydrocarbons. This has been found to cause soot to form and contaminate the product gases.
The present invention seeks to maximize the yield of usable CO and H.sub.2 obtained from the partial combustion of solid carbonaceous fuels by carrying out the partial combustion reaction in two stages, and, at the same time, minimize the amount of soot formed. Staged partial combustion processes have been previously proposed, e.g., see U.S. Pat. No. 2,886,421. However, in the staged partial combustion process described in that patent, the primary purpose of the second stage combustion is to supply heat to the first stage of the process and as a result the second stage is maintained at a temperature substantially the same or higher than the first stage.